Antenna systems are widely used for communications, radar, entertainment, and sensing uses. Many such antenna systems are in the forms of arras of elemental antennas, which are operated in a corporate or common fashion, to thereby achieve performance different from that which can be achieved with individual antenna elements, or for generating plural simultaneous antenna beams. The art of corporate beamformers is well advanced, and such beamformers are described in U.S. Pat. No. 5,025,485, issued Jun. 18, 1991 in the name of Csongor et al.; U.S. Pat. No. 5,017,927 issued May 21, 1991 in the name of Agrawal et al.; U.S. Pat. No. 5,274,386, issued Dec. 28, 1993 in the name of Pellon; U.S. Pat. No. 5,333,001 issued Jul. 26, 1994 in the name of Profera; U.S. Pat. No. 5,592,179, issued Jan. 7, 1997 in the name of Windyka; U.S. Pat. No. 6,014,372, issued Jan. 11, 2000 in the name of Kent et al.; U.S. Pat. No. 6,084,545, issued Jul. 4, 2000 in the name of Lier et al.; U.S. Pat. No. 6,087,974 issued Jul. 11, 2000 in the name of Yu; and U.S. Pat. No. 6,239,762, issued May 29, 2001 in the name of Lier.
Beamforming has in the past often been provided by complex three-dimensional hollow waveguide structures. However, such hollow waveguide structures are heavy, costly, and have limited bandwidth. In addition, waveguide structures require special treatment in order to provide the “crossovers” which may be required in some systems to achieve the correct phasing of the antennas of an array, as described in U.S. Pat. No. 5,274,839, issued Dec. 28, 1993 in the name of Kularajah et al.
Printed-circuit corporate beamformers are known for use with array antennas, but suffer from reduced power-handling capability relative to hollow-waveguide beamformers. However, by comparison with hollow-waveguide beamformers, printed-circuit beamformers are very inexpensive.
Improved beamformers are desired.